In conventional image sensors, an array of light-sensitive pixels located in the focal plane of a lens or lens system is used to evaluate the irradiance over a detection area. The pitch of the array determines spatial resolution. Each pixel will generate an analog signal to be amplified and A/D converted. In the absence of averaging, the intensity resolution such as the number of gray levels is limited by the resolution of the analog-to-digital converter (ADC); for example, an 8-bit ADC will be capable of 256 levels of gray. Greater intensity resolution may be obtained by averaging in space, over several pixels of a frame, or in time, over pixel values from several frames of a sequence of frames. Averaging in time can be used to reduce frame rate, and averaging in space will reduce spatial pixel resolution. Characteristically in such sensors, a sensor signal is linearly related to intensity of incident radiation.